Extract timer wrapper out of the session

utils/timer.go

@@ -0,0 +1,43 @@
+package utils
+
+import "time"
+
+// A Timer wrapper that behaves correctly when resetting
+type Timer struct {
+	t        *time.Timer
+	read     bool
+	deadline time.Time
+}
+
+// NewTimer creates a new timer that is not set
+func NewTimer() *Timer {
+	return &Timer{t: time.NewTimer(0)}
+}
+
+// Chan returns the channel of the wrapped timer
+func (t *Timer) Chan() <-chan time.Time {
+	return t.t.C
+}
+
+// Reset the timer, no matter whether the value was read or not
+func (t *Timer) Reset(deadline time.Time) {
+	if deadline.Equal(t.deadline) {
+		// No need to reset the timer
+		return
+	}
+
+	// We need to drain the timer if the value from its channel was not read yet.
+	// See https://groups.google.com/forum/#!topic/golang-dev/c9UUfASVPoU
+	if !t.t.Stop() && !t.read {
+		<-t.t.C
+	}
+	t.t.Reset(deadline.Sub(time.Now()))
+
+	t.read = false
+	t.deadline = deadline
+}
+
+// SetRead should be called after the value from the chan was read
+func (t *Timer) SetRead() {
+	t.read = true
+}

utils/timer_test.go

@@ -0,0 +1,45 @@
+package utils
+
+import (
+	"time"
+
+	. "github.com/onsi/ginkgo"
+	. "github.com/onsi/gomega"
+)
+
+var _ = Describe("Timer", func() {
+	const d = 10 * time.Millisecond
+
+	It("works", func() {
+		t := NewTimer()
+		t.Reset(time.Now().Add(d))
+		Eventually(t.Chan()).Should(Receive())
+	})
+
+	It("works multiple times with reading", func() {
+		t := NewTimer()
+		for i := 0; i < 10; i++ {
+			t.Reset(time.Now().Add(d))
+			Eventually(t.Chan()).Should(Receive())
+			t.SetRead()
+		}
+	})
+
+	It("works multiple times without reading", func() {
+		t := NewTimer()
+		for i := 0; i < 10; i++ {
+			t.Reset(time.Now().Add(d))
+			time.Sleep(d * 2)
+		}
+		Eventually(t.Chan()).Should(Receive())
+	})
+
+	It("works when resetting without expiration", func() {
+		t := NewTimer()
+		for i := 0; i < 10; i++ {
+			t.Reset(time.Now().Add(time.Hour))
+		}
+		t.Reset(time.Now().Add(d))
+		Eventually(t.Chan()).Should(Receive())
+	})
+})